How relevant is the ISP in DNS performance?

[Brad Knowles]

At 4:30 PM +0200 9/27/01, Nico De Ranter wrote:

>  Now, if I'm correct this means all dns queries will arrive on my primary
>  except if the primary is off-line then the secondary will take over.

	Nope.  For any remote nameserver that knows about your domain, 
they should keep track of which of your nameservers appears to be 
"faster", and direct most queries primarily towards that machine, 
failing over to the other if the first doesn't respond in time.  So, 
your server may appear to be "faster" to one site (and preferred by 
their nameserver), while your ISP may appear to be "faster" to 
another site (and preferred by their nameserver).  This isn't really 
anything you (or your ISP) has any control over.

	Not all nameservers implement this strategy, but most recent 
versions of BIND do, and BIND is the most common nameserver on the 
Internet.


	To answer the original question, the answer is "it depends".  It 
depends on how the zone is configured and who is hosting it, it 
depends on how their network routing is configured relative to where 
they place their nameservers, it depends on how those nameservers are 
configured, it depends on how heavily loaded those nameservers are, 
etc....

-- 
Brad Knowles, <brad.knowles at skynet.be>

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